In 1828, Robert Brown published the manuscript entitled “A brief account of microscopical observations made in the months of June, July and August 1827, on the particles contained in the pollen of plants; and on the general existence of active molecules in organic and inorganic bodies” in the Edinburgh new Philosophical Journal [download it in pdf format here]. He suspended some of the pollen grains of the species Clarkia pulchella in water and examined them closely, only to see them “filled with particles” of around 5 µm diameter that were “very evidently in motion”. ...